The 32-year-old joined the club in China’s northeast in January last year from Bayern Munich for five million euros and scored 12 goals in 26 matches.
Tianjin, who are coached by Wagner’s fellow German Uli Stielike, finished mid-table in last year’s CSL having battled against relegation in 2018.
“Together we played one of the best seasons in the club’s history and I’m proud that I could be part of it,” Wagner wrote in a letter to Tianjin fans.
Wagner, who scored five times in eight appearances for Germany, added: “Now I kindly ask for your understanding that I’m leaving the club for family reasons.
“I regret that we couldn’t see each other in 2020 again — but I wish you all the best in the future!”
The CSL season will begin five months late because of the coronavirus and with matches behind closed doors at neutral venues.
Fabio Cannavaro’s reigning champions Guangzhou Evergrande play FA Cup winners Shanghai Shenhua in the opener.
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